A container for containing drugs has conventionally been designed in such a manner that a drug-passage at a mouth portion of the container is closed with a rubber plug sufficiently sterilized and the container is simultaneously provided with a means for locking the rubber plug at the periphery of the mouth portion to thereby prevent any deterioration or quality-reduction of the drug or the like due to, for instance, air which flows into the container through the loosened portions for a push-fitted portion of the rubber plug and narrow gaps formed between the rubber plug and the mouth portion of the container in order to manage and transport a liquid content (drug) of a container while attending to sanitation. For instance, when a rubber plug is fitted into the mouth portion of a container containing a solution for injection, the rubber plug is push-fitted into a calking and fixing cap of, for instance, aluminum so that the cap and the rubber plug can protect the injection solution from any contamination of dust.
When a rubber plug is held in a caulking cap of aluminum and the rubber plug is inserted into the mouth portion of the container as discribed above, however, the drug solution inevitably comes in contact with the rubber plug. This may occasionally lead to dissolving of additives included in the rubber plug into the drug solution, formation of rubber waste and absorption and/or adsorption of drug components present in the solution on the rubber plug. For this reason, improvement of such a sealing means has been desired in order to ensure high quality of liquid drugs.
To solve the foregoing problems, there has been proposed a rubber plug having a surface coated with a fluoroplastics. Although such a fluoroplastic coating layer permits an increase in the hardness of the surface, it is often accompanied by the formation of wrinkle-like grooves during molding. Therefore, such a structure that a rubber plug is restrained by a caulking cap is insufficient in the tightening force and accordingly, a problem arises, that it is difficult to ensure sufficient sealing performance when the rubber plug is inserted into the mouth portion of a container.
Moreover, a container for keeping, for instance, a drug is mainly formed from a glass material and is fitted with a rubber plug for the purpose of sealing the container and a cap produced from, for instance, aluminum to prevent the rubber cap from falling off. Recently, it has become the general trend to make such a law that such a drug container should be disassembled and divided into combustible and incombustible parts after using the drug kept therein and prior to discarding the used container, from the viewpoint of environmental protection. Under such circumstances, there is a movement to replace glass containers as such drug containers with plastic ones in order to eliminate the need for the disassembly and classification of the waste after using them. However, it would still be necessary to remove the cap formed from, for instance, aluminum prior to discarding it, in spite of such change of materials.